16
2. Write the Read-File request with the section number and channel ID as shown in the
previous step.
3. Read the record data from the file response block.
4. Write an acknowledgment for the file. The file section pointer will be moved to the next
record.
5. Repeat steps 3-4 until all the section records are read.
Reading Multi-section Waveform Files
Waveform files can be read as conventional multi-section files in the order described above.
Another way is to take advantage of the fact that waveform files have a single read pointer
for all file sections, so you can read records of all the channels related to the same event at
once without repositioning the file pointer. The following gives a summary of steps for
reading waveform files:
1. If you want to begin reading a file from a particular record or from the first record, use
either the Set-File-Position request with the desired record sequence number, or the
Reset-File-Position request. Preset the section field to zero.
2. Write the Read-File request. Address you request to the first file section (its number is
always zero), or to the first file channel (if you know channel’s ID). If you use a channel
ID, preset the section number field to 0xFFFF.
3. Read the channel’s data from the file response block. Store the received record’s
sequence number.
4. Write the Read-File request for the next file section or channel using the stored record
sequence number. The file response block will be refilled with the data for the requested
channel that is related to the record with the same sequence number.
5. Repeat steps 3, 4 until all the channel records with the current sequence number are
read.
6. Write an acknowledgment. The file pointer will be moved to the next record.
Repeat steps 2-6 until all the file records are read.
Reading Real-time Waveforms
Real-time waveforms are accessed through the same transfer blocks just like the waveform
log files by addressing file 128. Writing the Read-File request for file 128 provides a
simultaneous capture of 6 real-time waveform records – three voltage and three current
waveforms – into a communication buffer that can be read through the common file
response block. The following gives a summary of steps for reading real-time waveforms:
1. Write the Read-File request for file 128. Address you request to the first file section (its
number is always zero), or to the first file channel (if you know channel’s ID). If you use
a channel ID, preset the section number field to 0xFFFF.
2. Read the channel’s data from the file response block.
3. Write the Read-File request for the next file section or channel. The file response block
will be refilled with the data for the requested channel.
4. Repeat steps 3, 4 until all the channel records are read.
5. Write an acknowledgment to release the buffer.
2.10 TCP Notification Client
The TCP notification client can establish connections with a remote Modbus/TCP server and
send notification messages either on events, or periodically on a time basis.
Notification messages are sent via a block of 24 Modbus registers using write function 16.
The following table shows the message exchange structure.
